A novel two-phase BPM drive system with high power density and low cost

A novel brushless permanent-magnet (BPM) motor drive system is proposed in this paper. The basic motor structure consists of a stator with four salient pole pieces and a six-pole permanent-magnet rotor. The proposed drive system, using four switches, fully utilizes the stator ampere turns by providing 180 electrical degree bipolar current conduction. Hence, the use of motor materials is maximized and very high power density is achieved. In addition, the quasi-square-wave back EMF and matching current waveshape guarantee minimum peak current stress on the drive. The low stress on the power devices and efficient use of active materials result in a drive system with a lower cost than conventional three-phase BPM drives of comparable output power. The advantages of the proposed system over three-phase BPM motor drives is illustrated using sizing analysis, finite-element analysis, time-domain simulations, and experimental studies. It can be expected that a variety of industrial applications will follow up on this new technology.